 Double Mersennes Prime Search

Welcome to the double Mersenne and Fermat factoring program. It is a fast GPU factoring program to find new factors
of small Fermat numbers (F26 to F223) and small double Mersenne numbers (MM31, MM61, MM89, MM107, and MM127).
It requires a Nvidia GPU with compute capabilities 2.0 or higher.

Visit http://www.fermatsearch.org to grab a range of k values for Fermat numbers.
Visit http://www.doublemersennes.org for the double Mersenne numbers.

Here is some of what you need to know:

mmff.exe is derived from mfaktc.exe. Like mfaktc.exe, mmff.exe uses a .ini file to control its behavior (mmff.ini).
You'll want to adjust GPUSievePrimes and GPUSieveSize for best performance.

Mmff.exe also uses a worktodo.txt file to control what numbers to factor.
For double-Mersennes, we tell mmff what double-Mersenne to try and factor.
For Fermat factoring, we tell mmff which factor candidates to try since a factor candidate might divide one of several Fermat numbers. Add this line to factor a double-Mersenne number:

MMFactor=exponent,minimum-bit-level-or-k-value,maximum-bit-level-or-k-value

Add this line to tell mmff which Fermat factor candidates (k*2N+1, k odd) to test:

FermatFactor=N,minimum-k-value,maximum-k-value

Since Mersenne factors are of the form 2*k*p + 1, the k-values for double-Mersennes yield factors 2*k*M(exponent)+1.
Fermat factors are of the form k*2N + 1 where k is odd.
A factor can divide any Fermat number from F12 up to F(N-2).

Example worktodo.txt entries:

```     MMFactor=127,179,180
FermatFactor=33,5460e9,5470e9
```

The first example looks for factors of MM127 from 2179 to 2180 (a big job that really should be split up into many k ranges.
The second example looks for any Fermat number with a factor between 5460000000000*233+1 and 5470000000000*233+1
(there is a known factor of F31 in that range).

To run the program once you've setup worktodo.txt and mmff.ini is very easy. On linux type:

```         ./mmff.exe >> my_output_file
```
Be sure to check the output file or results.txt for any new factors!

Mark Rodenkirch developed a program to search for bigger Fermat and DoubleMersenne factors it's called gmp-fermat or dm and can handle values from MM521 to MM23209.